[llvm] [AVR] Remove earlyclobber from LDDRdPtrQ (PR #85277)

[Ben Shi via llvm-commits]

benshi001 wrote:

Thanks for your great work! It looks good to me.

Just remove `Note that I'm not really sure the approach presented here is correct -
intuitively, ` in your commit message. Leave it as

```
This instruction shouldn't rely on `@earlyclobber`, since it doesn't have any input registers except for the implied `Y`, and `Y` is always marked as reserved in `AVRRegisterInfo::getReservedRegs`.
```

https://github.com/llvm/llvm-project/pull/85277